With the continuous improvement in living standards, people are increasingly concerned about their own health and the life or environmental factors that may affect the health. For example, passengers, pilots flying at high altitude or outdoor mountaineering, adventure users, or personnel working in a submarine or diving users need to know the surrounding air pressure or water pressure to determine whether the surrounding air pressure or water pressure conform to their own body adaptability. In the prior art, however, the air pressure or water pressure is generally measured using an independent device. This therefore increases the number of items carried by people during going out, reducing the convenience in carrying items.